1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member using a specific azo-based pigment.
2. Related Background Art
Organic pigments or dyes having a photoconductivity can be more readily synthesized than inorganic materials and have more variations from which compounds having a photoconductivity in an appropriate wavelength region can be selected. Thus, many photoconductive organic pigments and dyes have been so far proposed. As disclosed in, for example, U.S. Pat. Nos. 4,123,270; 4,247,614; 4,251,613; 4,251,614; 4,256,821; 4,260,672; 4,268,596; 4,278,747; 4,293,628, etc., electrophotographic photosensitive members using disazo pigments having a photoconductivity as a charge-generating material in a photosensitive layer, which is functionally separated into a charge generation layer and a charge transport layer, are known. Electrophotographic photosensitive members using such an organic photoconductive material can be produced by coating upon appropriate selection of a binder, and thus can be provided at a low cost with a very high productivity, and furthermore have an advantage of controlling a photosensitive wavelength resion as desired, upon selection of an organic pigment.
Photosensitive members having an organic pigment on an electroconductive layer so far known include:
(1) the one provided with a layer of a pigment as dispersed in an insulating binder on an electroconductive layer, as disclosed in Japanese Patent Publication No. 1667/1997 with the title "Electrophotographic plate;
(2) the one provided with layer of a pigment as dispersed in a charge transport material or a charge transport medium comprising a charge transport material and an insulating binder, which may be a charge transport material by itself, as disclosed in Japanese Patent Application Laid-open No. 30328/1972 with the title "Electrophotographic plate" and Japanese Patent Application Laid-open No. 18545/1972 with the title "Electrophotographic process";
(3) the one comprising an electroconductive layer, a charge generation layer containing an organic pigment and a charge transport layer, as disclosed in Japanese Patent Application Laid-open No. 105537/1974 with the title "Electrophotographic plate";
(4) the one provided with a charge transfer complex containing an organic pigment, as shown in Japanese Patent Application Laid-open No. 91648/1974 with the title "Photoconductive member"; and
(5) others.
Among the photoconductive azo pigments used in such electrophotographic photosensitive members, disazo pigments having a benzoxazole skeleton, as disclosed in Japanese Patent Applications Laid-open Nos. 116039/1981 (=U.S. Pat. No. 4,356,243); 63,541/1982; 63542/1982 and 63549/1982; disazo pigments having an benzthiazole skeleton, as disclosed in Japanese Patent Application Laid-open No. 63537/1982; and disazo pigments having a benzimidazole skeleton, as disclosed in Japanese Patent Applications Laid-open nos. 49,950/1982; 78,542/1982; and 90,632/1982 are said to have distinguished characteristics, but are still keenly required to meet higher speed of a copying machine using a photosensitive member or lower cost thereof, which can be attained with respect to the lens, light source, power source for the light source, etc. by higher sensitization of the photosensitive member. In these circumstances, the photosensitive members are still now required for much higher sensitization.